MODELLING THE EFFECTS OF SHOAL ATTACHMENT ON DUNE GROWTH

A cellular automata model is used to evaluate the impact of shoal attachment processes on dune growth. We explore ten different idealized scenarios of beach width changes due to shoal attachment related to the magnitude of the shoal-driven beach width increase and the rate of dispersion alongshore. For all scenarios, shoals attach the coast with a cyclic period of 15 years in an average beach width of 100 meters. Simulations were carried out for a model time of 90 years. Results show that in only three scenarios, shoal attachment yielded a significant increase in dune growth. Scenarios that significantly changed dune growth presented the slowest rate of spreading and the three largest beach width increase tested. This suggests that local change in dune growth due to shoal attachment are closely related to the shoal capacity of significantly increasing beach width and the longshore capacity of sediment transport.